This invention relates to a dual coil electromagnetic pickup assembly for stringed musical instrument, consisting of a first longitudinal structure, designed to support the first longitudinal coil, the said structure and coil having a first end and a second end, and a second longitudinal structure to support the second longitudinal coil, also having a first end and a second end. Both said coils consist of a magnetically permeable core region, and the said first coil has a magnetically permeable core region having the opposite polarity as opposed to the secondary coil. The coils are then connected in parallel or in series in such a way that they eliminate the extraneous noise or hum of each other.
The electromagnetic pickup described in the present invention serves particularly well as a pickup of an electric guitar, but can also be fitted to other musical instruments, such as a banjo etc.
Said dual coil electromagnetic pickups are well known to those working in the field. As opposed to single coil electromagnetic pickups, said dual coil pickups do not, or at least not notably, work as an antenna to pickup extraneous noise or hum. Therefore frequencies such as the 60 cycle hum generated by electronic equipment are not picked up and amplified to audible noise. These dual coil pickups are called humcancelling pickups or “humbuckers”. Humbuckers consist of at least two coils connected out of phase to each other, so that the noise or the hum picked up by the two coils cancel one another out.
The original noise cancelling pickup design in the prior art was made by Lover and patented as U.S. Pat. No. 2,896,491. The disadvantage of the Lover side-by-side arrangement is that it senses the vibration of the string from a wider area in the string. This causes frequency loss and muted overall sound lacking clarity and detail. Humbuckers often lack the wide dynamic range of the single coil design.
It is known that there are musical instrument pickups that have two coils positioned end to end to each other, having opposite magnetic polarities and connected out of phase to each other. The first coil is placed under the strings so that it senses about half of the strings and the other coil is placed so that it senses the rest of the strings. The disadvantage of this design is that a “dead” area is created in the middle of the pickup. It is known that guitar players use a technique called string bending, where a string is pushed by the fingers to raise the frequency. By doing so, the string changes its position in relation to the pickup. If the string is bent so that it is positioned straight above the point where the ends of the coils meet and where the two magnetic fields meet, an extremely weak, out of phase signal is produced. Therefore the pickup of this design does not have a uniform output level throughout its length. The said problem does not appear in musical instruments the strings of which are usually not bent, such as an electric bass guitar.
Because the Lover design humbuckers have two coils positioned in a side by side manner, they are significantly wider in size compared to those that have only a single coil. If a pickup consisting of two side by side coils is to be installed on a guitar having routings and/or a pickguard made for a single coil sized pickup, significant changes to the instrument have to be made. These changes affect the value of the instrument in an undesirable way, especially if a vintage guitar is in question. One of the most popular electric guitar models is the Fender Stratocaster designed by Leo Fender, which has a three pickup design. It has remained almost unchanged to this day. The guitar model in question still consists of three single coil sized pickups. Therefore it still has the routings in the body cut to fit three single coil sized pickups. The pickups of these types of guitars have remained single coiled, because humcancelling pickups that would be of the same size and would not require major changes to the classic look of the guitar, and would have the same tonal balance, have not been possible yet.
Another well-known practice is to place two coils so that one coil senses about half of the instrument's strings and the other one senses the rest of the strings. The coils have a different axis and have been placed so that the coils and their core regions are far enough from each other, so that the magnetic fields do not interfere with each other (U.S. Pat. No. D319,456 issued to Fender). They also do not fit the existing routings and pickguard cut outs because of the two different longitudinal axes of the coils.
So the problem is how to make an electromagnetic pickup that would have the same clarity, dynamics and tonal balance as a single coil pickup, but would still have significantly less extraneous noise and hum.
One solution to make a humcancelling single-coil-sized pickup is to stack two coils on top of each other (U.S. Pat. No. 4,442,749 issued to Dimarzio et al.; U.S. Pat. No. 4,524,667 issued to Duncan; U.S. Pat. No. 5,668,520 issued to Kinman; U.S. Pat. No. 6,291,759 issued to Turner). But in order to fit the two coils on the guitar, the two coils together have to be approximately of the same height as that of the coil of a single coil pickup. Usually the uppermost coil of this type of pickup is the string vibration sensing coil and the lower coil's only function is to eliminate unwanted noise picked up by the uppermost coil. In other words, the lower coil is not designed to produce any audible sound. Since the uppermost coil in this design is only about half of the height of the entire coil in the single coil design, the sound produced by it differs from the sought after sound of a single coil. It is also preferable to have the two stacked coils magnetically isolated from each other to prevent an out of phase sound. This has been achieved by placing a U-shaped steel plate under the uppermost coil to direct the magnetic field. This plate also has its effect on the sound.
All known ways of making humcancelling single coil sized pickups have failed to produce the clear and dynamic sound of a single coil pickup or they have had an unbalanced output level throughout the length of the pickup.